A mobile apparatus in a mobile communication system transitions to some power saving states (Battery Efficient states) after completion of transmission and reception of data signals in order to reduce battery power consumption. Operating states of the mobile apparatus are managed by a controller (for example, a radio network controller (RNC) in a W-CDMA system). When the mobile apparatus changes the operating state, the mobile apparatus has to receive an indication for it from the controller. After completion of transmission and reception in a dedicated channel (DCH), the mobile apparatus transmits a state transition request signal to request transition to a power saving state. In the W-CDMA system, the state transition request signal is referred to as an RRC SIGNALING CONNECTION RELEASE INDICATION. The mobile apparatus can transition to the power saving state by receiving an indication from the controller or a network (NW). The power saving state is an idle state, a PCH state (Cell_PCH/URA_PCH), a FACH (Forward Access Channel) state for use of a FACH and so on. In the mobile communication system, a function to enable the mobile apparatus to transition to any of the power saving states after releasing the dedicated channel (DCH) to save battery energy in the mobile apparatus is called a Fast Dormancy function. See 3GPP TS25.331 v8.6.0 for the function, for example.